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[dragonfly.git] / sys / net / altq / altq_hfsc.c

/*      $KAME: altq_hfsc.c,v 1.25 2004/04/17 10:54:48 kjc Exp $ */
/*      $DragonFly: src/sys/net/altq/altq_hfsc.c,v 1.9 2008/05/14 11:59:23 sephe Exp $ */

/*
 * Copyright (c) 1997-1999 Carnegie Mellon University. All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this software and
 * its documentation is hereby granted (including for commercial or
 * for-profit use), provided that both the copyright notice and this
 * permission notice appear in all copies of the software, derivative
 * works, or modified versions, and any portions thereof.
 *
 * THIS SOFTWARE IS EXPERIMENTAL AND IS KNOWN TO HAVE BUGS, SOME OF
 * WHICH MAY HAVE SERIOUS CONSEQUENCES.  CARNEGIE MELLON PROVIDES THIS
 * SOFTWARE IN ITS ``AS IS'' CONDITION, AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
 * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 *
 * Carnegie Mellon encourages (but does not require) users of this
 * software to return any improvements or extensions that they make,
 * and to grant Carnegie Mellon the rights to redistribute these
 * changes without encumbrance.
 */
/*
 * H-FSC is described in Proceedings of SIGCOMM'97,
 * "A Hierarchical Fair Service Curve Algorithm for Link-Sharing,
 * Real-Time and Priority Service"
 * by Ion Stoica, Hui Zhang, and T. S. Eugene Ng.
 *
 * Oleg Cherevko <olwi@aq.ml.com.ua> added the upperlimit for link-sharing.
 * when a class has an upperlimit, the fit-time is computed from the
 * upperlimit service curve.  the link-sharing scheduler does not schedule
 * a class whose fit-time exceeds the current time.
 */

#include "opt_altq.h"
#include "opt_inet.h"
#include "opt_inet6.h"

#ifdef ALTQ_HFSC  /* hfsc is enabled by ALTQ_HFSC option in opt_altq.h */

#include <sys/param.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/systm.h>
#include <sys/errno.h>
#include <sys/queue.h>
#include <sys/thread.h>

#include <net/if.h>
#include <net/ifq_var.h>
#include <netinet/in.h>

#include <net/pf/pfvar.h>
#include <net/altq/altq.h>
#include <net/altq/altq_hfsc.h>

#include <sys/thread2.h>

/*
 * function prototypes
 */
static int      hfsc_clear_interface(struct hfsc_if *);
static int      hfsc_request(struct ifaltq *, int, void *);
static void     hfsc_purge(struct hfsc_if *);
static struct hfsc_class *hfsc_class_create(struct hfsc_if *,
                                            struct service_curve *,
                                            struct service_curve *,
                                            struct service_curve *,
                                            struct hfsc_class *, int, int, int);
static int      hfsc_class_destroy(struct hfsc_class *);
static struct hfsc_class *hfsc_nextclass(struct hfsc_class *);
static int      hfsc_enqueue(struct ifaltq *, struct mbuf *,
                             struct altq_pktattr *);
static struct mbuf *hfsc_dequeue(struct ifaltq *, struct mbuf *, int);

static int      hfsc_addq(struct hfsc_class *, struct mbuf *);
static struct mbuf *hfsc_getq(struct hfsc_class *);
static struct mbuf *hfsc_pollq(struct hfsc_class *);
static void     hfsc_purgeq(struct hfsc_class *);

static void     update_cfmin(struct hfsc_class *);
static void     set_active(struct hfsc_class *, int);
static void     set_passive(struct hfsc_class *);

static void     init_ed(struct hfsc_class *, int);
static void     update_ed(struct hfsc_class *, int);
static void     update_d(struct hfsc_class *, int);
static void     init_vf(struct hfsc_class *, int);
static void     update_vf(struct hfsc_class *, int, uint64_t);
static ellist_t *ellist_alloc(void);
static void     ellist_destroy(ellist_t *);
static void     ellist_insert(struct hfsc_class *);
static void     ellist_remove(struct hfsc_class *);
static void     ellist_update(struct hfsc_class *);
struct hfsc_class *ellist_get_mindl(ellist_t *, uint64_t);
static actlist_t *actlist_alloc(void);
static void     actlist_destroy(actlist_t *);
static void     actlist_insert(struct hfsc_class *);
static void     actlist_remove(struct hfsc_class *);
static void     actlist_update(struct hfsc_class *);

static struct hfsc_class *actlist_firstfit(struct hfsc_class *, uint64_t);

static __inline uint64_t        seg_x2y(uint64_t, uint64_t);
static __inline uint64_t        seg_y2x(uint64_t, uint64_t);
static __inline uint64_t        m2sm(u_int);
static __inline uint64_t        m2ism(u_int);
static __inline uint64_t        d2dx(u_int);
static u_int                    sm2m(uint64_t);
static u_int                    dx2d(uint64_t);

static void     sc2isc(struct service_curve *, struct internal_sc *);
static void     rtsc_init(struct runtime_sc *, struct internal_sc *,
                          uint64_t, uint64_t);
static uint64_t rtsc_y2x(struct runtime_sc *, uint64_t);
static uint64_t rtsc_x2y(struct runtime_sc *, uint64_t);
static void     rtsc_min(struct runtime_sc *, struct internal_sc *,
                         uint64_t, uint64_t);

static void     get_class_stats(struct hfsc_classstats *, struct hfsc_class *);
static struct hfsc_class *clh_to_clp(struct hfsc_if *, uint32_t);

/*
 * macros
 */
#define is_a_parent_class(cl)   ((cl)->cl_children != NULL)

#define HT_INFINITY     0xffffffffffffffffLL    /* infinite time value */

int
hfsc_pfattach(struct pf_altq *a, struct ifaltq *ifq)
{
        return altq_attach(ifq, ALTQT_HFSC, a->altq_disc,
            hfsc_enqueue, hfsc_dequeue, hfsc_request, NULL, NULL);
}

int
hfsc_add_altq(struct pf_altq *a)
{
        struct hfsc_if *hif;
        struct ifnet *ifp;

        if ((ifp = ifunit(a->ifname)) == NULL)
                return (EINVAL);
        if (!ifq_is_ready(&ifp->if_snd))
                return (ENODEV);

        hif = kmalloc(sizeof(struct hfsc_if), M_ALTQ, M_WAITOK | M_ZERO);

        hif->hif_eligible = ellist_alloc();
        hif->hif_ifq = &ifp->if_snd;
        ifq_purge(&ifp->if_snd);

        /* keep the state in pf_altq */
        a->altq_disc = hif;

        return (0);
}

int
hfsc_remove_altq(struct pf_altq *a)
{
        struct hfsc_if *hif;

        if ((hif = a->altq_disc) == NULL)
                return (EINVAL);
        a->altq_disc = NULL;

        hfsc_clear_interface(hif);
        hfsc_class_destroy(hif->hif_rootclass);

        ellist_destroy(hif->hif_eligible);

        kfree(hif, M_ALTQ);

        return (0);
}

static int
hfsc_add_queue_locked(struct pf_altq *a, struct hfsc_if *hif)
{
        struct hfsc_class *cl, *parent;
        struct hfsc_opts *opts;
        struct service_curve rtsc, lssc, ulsc;

        KKASSERT(a->qid != 0);

        opts = &a->pq_u.hfsc_opts;

        if (a->parent_qid == HFSC_NULLCLASS_HANDLE && hif->hif_rootclass == NULL)
                parent = NULL;
        else if ((parent = clh_to_clp(hif, a->parent_qid)) == NULL)
                return (EINVAL);

        if (clh_to_clp(hif, a->qid) != NULL)
                return (EBUSY);

        rtsc.m1 = opts->rtsc_m1;
        rtsc.d  = opts->rtsc_d;
        rtsc.m2 = opts->rtsc_m2;
        lssc.m1 = opts->lssc_m1;
        lssc.d  = opts->lssc_d;
        lssc.m2 = opts->lssc_m2;
        ulsc.m1 = opts->ulsc_m1;
        ulsc.d  = opts->ulsc_d;
        ulsc.m2 = opts->ulsc_m2;

        cl = hfsc_class_create(hif, &rtsc, &lssc, &ulsc, parent, a->qlimit,
                               opts->flags, a->qid);
        if (cl == NULL)
                return (ENOMEM);

        return (0);
}

int
hfsc_add_queue(struct pf_altq *a)
{
        struct hfsc_if *hif;
        struct ifaltq *ifq;
        int error;

        if (a->qid == 0)
                return (EINVAL);

        /* XXX not MP safe */
        if ((hif = a->altq_disc) == NULL)
                return (EINVAL);
        ifq = hif->hif_ifq;

        ALTQ_LOCK(ifq);
        error = hfsc_add_queue_locked(a, hif);
        ALTQ_UNLOCK(ifq);

        return error;
}

static int
hfsc_remove_queue_locked(struct pf_altq *a, struct hfsc_if *hif)
{
        struct hfsc_class *cl;

        if ((cl = clh_to_clp(hif, a->qid)) == NULL)
                return (EINVAL);

        return (hfsc_class_destroy(cl));
}

int
hfsc_remove_queue(struct pf_altq *a)
{
        struct hfsc_if *hif;
        struct ifaltq *ifq;
        int error;

        /* XXX not MP safe */
        if ((hif = a->altq_disc) == NULL)
                return (EINVAL);
        ifq = hif->hif_ifq;

        ALTQ_LOCK(ifq);
        error = hfsc_remove_queue_locked(a, hif);
        ALTQ_UNLOCK(ifq);

        return error;
}

int
hfsc_getqstats(struct pf_altq *a, void *ubuf, int *nbytes)
{
        struct hfsc_if *hif;
        struct hfsc_class *cl;
        struct hfsc_classstats stats;
        struct ifaltq *ifq;
        int error = 0;

        if (*nbytes < sizeof(stats))
                return (EINVAL);

        /* XXX not MP safe */
        if ((hif = altq_lookup(a->ifname, ALTQT_HFSC)) == NULL)
                return (EBADF);
        ifq = hif->hif_ifq;

        ALTQ_LOCK(ifq);

        if ((cl = clh_to_clp(hif, a->qid)) == NULL) {
                ALTQ_UNLOCK(ifq);
                return (EINVAL);
        }

        get_class_stats(&stats, cl);

        ALTQ_UNLOCK(ifq);

        if ((error = copyout((caddr_t)&stats, ubuf, sizeof(stats))) != 0)
                return (error);
        *nbytes = sizeof(stats);
        return (0);
}

/*
 * bring the interface back to the initial state by discarding
 * all the filters and classes except the root class.
 */
static int
hfsc_clear_interface(struct hfsc_if *hif)
{
        struct hfsc_class *cl;

        if (hif->hif_rootclass == NULL)
                return (0);


        /* clear out the classes */
        while ((cl = hif->hif_rootclass->cl_children) != NULL) {
                /*
                 * remove the first leaf class found in the hierarchy
                 * then start over
                 */
                for (; cl != NULL; cl = hfsc_nextclass(cl)) {
                        if (!is_a_parent_class(cl)) {
                                hfsc_class_destroy(cl);
                                break;
                        }
                }
        }

        return (0);
}

static int
hfsc_request(struct ifaltq *ifq, int req, void *arg)
{
        struct hfsc_if *hif = (struct hfsc_if *)ifq->altq_disc;

        crit_enter();
        switch (req) {
        case ALTRQ_PURGE:
                hfsc_purge(hif);
                break;
        }
        crit_exit();
        return (0);
}

/* discard all the queued packets on the interface */
static void
hfsc_purge(struct hfsc_if *hif)
{
        struct hfsc_class *cl;

        for (cl = hif->hif_rootclass; cl != NULL; cl = hfsc_nextclass(cl)) {
                if (!qempty(cl->cl_q))
                        hfsc_purgeq(cl);
        }
        if (ifq_is_enabled(hif->hif_ifq))
                hif->hif_ifq->ifq_len = 0;
}

struct hfsc_class *
hfsc_class_create(struct hfsc_if *hif, struct service_curve *rsc,
                  struct service_curve *fsc, struct service_curve *usc,
                  struct hfsc_class *parent, int qlimit, int flags, int qid)
{
        struct hfsc_class *cl, *p;
        int i;

        if (hif->hif_classes >= HFSC_MAX_CLASSES)
                return (NULL);

#ifndef ALTQ_RED
        if (flags & HFCF_RED) {
#ifdef ALTQ_DEBUG
                kprintf("hfsc_class_create: RED not configured for HFSC!\n");
#endif
                return (NULL);
        }
#endif

        cl = kmalloc(sizeof(*cl), M_ALTQ, M_WAITOK | M_ZERO);
        cl->cl_q = kmalloc(sizeof(*cl->cl_q), M_ALTQ, M_WAITOK | M_ZERO);
        cl->cl_actc = actlist_alloc();

        if (qlimit == 0)
                qlimit = 50;  /* use default */
        qlimit(cl->cl_q) = qlimit;
        qtype(cl->cl_q) = Q_DROPTAIL;
        qlen(cl->cl_q) = 0;
        cl->cl_flags = flags;
#ifdef ALTQ_RED
        if (flags & (HFCF_RED|HFCF_RIO)) {
                int red_flags, red_pkttime;
                u_int m2;

                m2 = 0;
                if (rsc != NULL && rsc->m2 > m2)
                        m2 = rsc->m2;
                if (fsc != NULL && fsc->m2 > m2)
                        m2 = fsc->m2;
                if (usc != NULL && usc->m2 > m2)
                        m2 = usc->m2;

                red_flags = 0;
                if (flags & HFCF_ECN)
                        red_flags |= REDF_ECN;
#ifdef ALTQ_RIO
                if (flags & HFCF_CLEARDSCP)
                        red_flags |= RIOF_CLEARDSCP;
#endif
                if (m2 < 8)
                        red_pkttime = 1000 * 1000 * 1000; /* 1 sec */
                else
                        red_pkttime = (int64_t)hif->hif_ifq->altq_ifp->if_mtu
                                * 1000 * 1000 * 1000 / (m2 / 8);
                if (flags & HFCF_RED) {
                        cl->cl_red = red_alloc(0, 0,
                            qlimit(cl->cl_q) * 10/100,
                            qlimit(cl->cl_q) * 30/100,
                            red_flags, red_pkttime);
                        if (cl->cl_red != NULL)
                                qtype(cl->cl_q) = Q_RED;
                }
#ifdef ALTQ_RIO
                else {
                        cl->cl_red = (red_t *)rio_alloc(0, NULL,
                            red_flags, red_pkttime);
                        if (cl->cl_red != NULL)
                                qtype(cl->cl_q) = Q_RIO;
                }
#endif
        }
#endif /* ALTQ_RED */

        if (rsc != NULL && (rsc->m1 != 0 || rsc->m2 != 0)) {
                cl->cl_rsc = kmalloc(sizeof(*cl->cl_rsc), M_ALTQ, M_WAITOK);
                sc2isc(rsc, cl->cl_rsc);
                rtsc_init(&cl->cl_deadline, cl->cl_rsc, 0, 0);
                rtsc_init(&cl->cl_eligible, cl->cl_rsc, 0, 0);
        }
        if (fsc != NULL && (fsc->m1 != 0 || fsc->m2 != 0)) {
                cl->cl_fsc = kmalloc(sizeof(*cl->cl_fsc), M_ALTQ, M_WAITOK);
                if (cl->cl_fsc == NULL)
                        goto err_ret;
                sc2isc(fsc, cl->cl_fsc);
                rtsc_init(&cl->cl_virtual, cl->cl_fsc, 0, 0);
        }
        if (usc != NULL && (usc->m1 != 0 || usc->m2 != 0)) {
                cl->cl_usc = kmalloc(sizeof(*cl->cl_usc), M_ALTQ, M_WAITOK);
                if (cl->cl_usc == NULL)
                        goto err_ret;
                sc2isc(usc, cl->cl_usc);
                rtsc_init(&cl->cl_ulimit, cl->cl_usc, 0, 0);
        }

        cl->cl_id = hif->hif_classid++;
        cl->cl_handle = qid;
        cl->cl_hif = hif;
        cl->cl_parent = parent;

        crit_enter();
        hif->hif_classes++;

        /*
         * find a free slot in the class table.  if the slot matching
         * the lower bits of qid is free, use this slot.  otherwise,
         * use the first free slot.
         */
        i = qid % HFSC_MAX_CLASSES;
        if (hif->hif_class_tbl[i] == NULL)
                hif->hif_class_tbl[i] = cl;
        else {
                for (i = 0; i < HFSC_MAX_CLASSES; i++) {
                        if (hif->hif_class_tbl[i] == NULL) {
                                hif->hif_class_tbl[i] = cl;
                                break;
                        }
                }
                if (i == HFSC_MAX_CLASSES) {
                        crit_exit();
                        goto err_ret;
                }
        }

        if (flags & HFCF_DEFAULTCLASS)
                hif->hif_defaultclass = cl;

        if (parent == NULL) {
                /* this is root class */
                hif->hif_rootclass = cl;
        } else if (parent->cl_children == NULL) {
                /* add this class to the children list of the parent */
                parent->cl_children = cl;
        } else {
                p = parent->cl_children;
                while (p->cl_siblings != NULL)
                        p = p->cl_siblings;
                p->cl_siblings = cl;
        }
        crit_exit();

        return (cl);

 err_ret:
        if (cl->cl_actc != NULL)
                actlist_destroy(cl->cl_actc);
        if (cl->cl_red != NULL) {
#ifdef ALTQ_RIO
                if (q_is_rio(cl->cl_q))
                        rio_destroy((rio_t *)cl->cl_red);
#endif
#ifdef ALTQ_RED
                if (q_is_red(cl->cl_q))
                        red_destroy(cl->cl_red);
#endif
        }
        if (cl->cl_fsc != NULL)
                kfree(cl->cl_fsc, M_ALTQ);
        if (cl->cl_rsc != NULL)
                kfree(cl->cl_rsc, M_ALTQ);
        if (cl->cl_usc != NULL)
                kfree(cl->cl_usc, M_ALTQ);
        if (cl->cl_q != NULL)
                kfree(cl->cl_q, M_ALTQ);
        kfree(cl, M_ALTQ);
        return (NULL);
}

static int
hfsc_class_destroy(struct hfsc_class *cl)
{
        int i;

        if (cl == NULL)
                return (0);

        if (is_a_parent_class(cl))
                return (EBUSY);

        crit_enter();

        if (!qempty(cl->cl_q))
                hfsc_purgeq(cl);

        if (cl->cl_parent == NULL) {
                /* this is root class */
        } else {
                struct hfsc_class *p = cl->cl_parent->cl_children;

                if (p == cl) {
                        cl->cl_parent->cl_children = cl->cl_siblings;
                } else {
                        do {
                                if (p->cl_siblings == cl) {
                                        p->cl_siblings = cl->cl_siblings;
                                        break;
                                }
                        } while ((p = p->cl_siblings) != NULL);
                }
                KKASSERT(p != NULL);
        }

        for (i = 0; i < HFSC_MAX_CLASSES; i++) {
                if (cl->cl_hif->hif_class_tbl[i] == cl) {
                        cl->cl_hif->hif_class_tbl[i] = NULL;
                        break;
                }
        }

        cl->cl_hif->hif_classes--;
        crit_exit();

        actlist_destroy(cl->cl_actc);

        if (cl->cl_red != NULL) {
#ifdef ALTQ_RIO
                if (q_is_rio(cl->cl_q))
                        rio_destroy((rio_t *)cl->cl_red);
#endif
#ifdef ALTQ_RED
                if (q_is_red(cl->cl_q))
                        red_destroy(cl->cl_red);
#endif
        }

        if (cl == cl->cl_hif->hif_rootclass)
                cl->cl_hif->hif_rootclass = NULL;
        if (cl == cl->cl_hif->hif_defaultclass)
                cl->cl_hif->hif_defaultclass = NULL;

        if (cl->cl_usc != NULL)
                kfree(cl->cl_usc, M_ALTQ);
        if (cl->cl_fsc != NULL)
                kfree(cl->cl_fsc, M_ALTQ);
        if (cl->cl_rsc != NULL)
                kfree(cl->cl_rsc, M_ALTQ);
        kfree(cl->cl_q, M_ALTQ);
        kfree(cl, M_ALTQ);

        return (0);
}

/*
 * hfsc_nextclass returns the next class in the tree.
 *   usage:
 *      for (cl = hif->hif_rootclass; cl != NULL; cl = hfsc_nextclass(cl))
 *              do_something;
 */
static struct hfsc_class *
hfsc_nextclass(struct hfsc_class *cl)
{
        if (cl->cl_children != NULL) {
                cl = cl->cl_children;
        } else if (cl->cl_siblings != NULL) {
                cl = cl->cl_siblings;
        } else {
                while ((cl = cl->cl_parent) != NULL) {
                        if (cl->cl_siblings != NULL) {
                                cl = cl->cl_siblings;
                                break;
                        }
                }
        }

        return (cl);
}

/*
 * hfsc_enqueue is an enqueue function to be registered to
 * (*altq_enqueue) in struct ifaltq.
 */
static int
hfsc_enqueue(struct ifaltq *ifq, struct mbuf *m, struct altq_pktattr *pktattr)
{
        struct hfsc_if  *hif = (struct hfsc_if *)ifq->altq_disc;
        struct hfsc_class *cl;
        int len;

        /* grab class set by classifier */
        if ((m->m_flags & M_PKTHDR) == 0) {
                /* should not happen */
                if_printf(ifq->altq_ifp, "altq: packet does not have pkthdr\n");
                m_freem(m);
                return (ENOBUFS);
        }
        crit_enter();
        if (m->m_pkthdr.fw_flags & ALTQ_MBUF_TAGGED)
                cl = clh_to_clp(hif, m->m_pkthdr.altq_qid);
        else
                cl = NULL;
        if (cl == NULL || is_a_parent_class(cl)) {
                cl = hif->hif_defaultclass;
                if (cl == NULL) {
                        m_freem(m);
                        crit_exit();
                        return (ENOBUFS);
                }
        }
        cl->cl_pktattr = NULL;
        len = m_pktlen(m);
        if (hfsc_addq(cl, m) != 0) {
                /* drop occurred.  mbuf was freed in hfsc_addq. */
                PKTCNTR_ADD(&cl->cl_stats.drop_cnt, len);
                crit_exit();
                return (ENOBUFS);
        }
        ifq->ifq_len++;
        cl->cl_hif->hif_packets++;

        /* successfully queued. */
        if (qlen(cl->cl_q) == 1)
                set_active(cl, m_pktlen(m));
        crit_exit();
        return (0);
}

/*
 * hfsc_dequeue is a dequeue function to be registered to
 * (*altq_dequeue) in struct ifaltq.
 *
 * note: ALTDQ_POLL returns the next packet without removing the packet
 *      from the queue.  ALTDQ_REMOVE is a normal dequeue operation.
 *      ALTDQ_REMOVE must return the same packet if called immediately
 *      after ALTDQ_POLL.
 */
static struct mbuf *
hfsc_dequeue(struct ifaltq *ifq, struct mbuf *mpolled, int op)
{
        struct hfsc_if  *hif = (struct hfsc_if *)ifq->altq_disc;
        struct hfsc_class *cl;
        struct mbuf *m;
        int len, next_len;
        int realtime = 0;
        uint64_t cur_time;

        if (hif->hif_packets == 0) {
                /* no packet in the tree */
                return (NULL);
        }

        crit_enter();
        cur_time = read_machclk();

        if (op == ALTDQ_REMOVE && hif->hif_pollcache != NULL) {
                cl = hif->hif_pollcache;
                hif->hif_pollcache = NULL;
                /* check if the class was scheduled by real-time criteria */
                if (cl->cl_rsc != NULL)
                        realtime = (cl->cl_e <= cur_time);
        } else {
                /*
                 * if there are eligible classes, use real-time criteria.
                 * find the class with the minimum deadline among
                 * the eligible classes.
                 */
                if ((cl = ellist_get_mindl(hif->hif_eligible, cur_time)) != NULL) {
                        realtime = 1;
                } else {
#ifdef ALTQ_DEBUG
                        int fits = 0;
#endif
                        /*
                         * use link-sharing criteria
                         * get the class with the minimum vt in the hierarchy
                         */
                        cl = hif->hif_rootclass;
                        while (is_a_parent_class(cl)) {

                                cl = actlist_firstfit(cl, cur_time);
                                if (cl == NULL) {
#ifdef ALTQ_DEBUG
                                        if (fits > 0)
                                                kprintf("%d fit but none found\n",fits);
#endif
                                        m = NULL;
                                        goto done;
                                }
                                /*
                                 * update parent's cl_cvtmin.
                                 * don't update if the new vt is smaller.
                                 */
                                if (cl->cl_parent->cl_cvtmin < cl->cl_vt)
                                        cl->cl_parent->cl_cvtmin = cl->cl_vt;
#ifdef ALTQ_DEBUG
                                fits++;
#endif
                        }
                }

                if (op == ALTDQ_POLL) {
                        hif->hif_pollcache = cl;
                        m = hfsc_pollq(cl);
                        goto done;
                }
        }

        m = hfsc_getq(cl);
        if (m == NULL)
                panic("hfsc_dequeue:");
        len = m_pktlen(m);
        cl->cl_hif->hif_packets--;
        ifq->ifq_len--;
        PKTCNTR_ADD(&cl->cl_stats.xmit_cnt, len);

        update_vf(cl, len, cur_time);
        if (realtime)
                cl->cl_cumul += len;

        if (!qempty(cl->cl_q)) {
                if (cl->cl_rsc != NULL) {
                        /* update ed */
                        next_len = m_pktlen(qhead(cl->cl_q));

                        if (realtime)
                                update_ed(cl, next_len);
                        else
                                update_d(cl, next_len);
                }
        } else {
                /* the class becomes passive */
                set_passive(cl);
        }
done:
        crit_exit();
        KKASSERT(mpolled == NULL || m == mpolled);
        return (m);
}

static int
hfsc_addq(struct hfsc_class *cl, struct mbuf *m)
{

#ifdef ALTQ_RIO
        if (q_is_rio(cl->cl_q))
                return rio_addq((rio_t *)cl->cl_red, cl->cl_q,
                                m, cl->cl_pktattr);
#endif
#ifdef ALTQ_RED
        if (q_is_red(cl->cl_q))
                return red_addq(cl->cl_red, cl->cl_q, m, cl->cl_pktattr);
#endif
        if (qlen(cl->cl_q) >= qlimit(cl->cl_q)) {
                m_freem(m);
                return (-1);
        }

        if (cl->cl_flags & HFCF_CLEARDSCP)
                write_dsfield(m, cl->cl_pktattr, 0);

        _addq(cl->cl_q, m);

        return (0);
}

static struct mbuf *
hfsc_getq(struct hfsc_class *cl)
{
#ifdef ALTQ_RIO
        if (q_is_rio(cl->cl_q))
                return rio_getq((rio_t *)cl->cl_red, cl->cl_q);
#endif
#ifdef ALTQ_RED
        if (q_is_red(cl->cl_q))
                return red_getq(cl->cl_red, cl->cl_q);
#endif
        return _getq(cl->cl_q);
}

static struct mbuf *
hfsc_pollq(struct hfsc_class *cl)
{
        return qhead(cl->cl_q);
}

static void
hfsc_purgeq(struct hfsc_class *cl)
{
        struct mbuf *m;

        if (qempty(cl->cl_q))
                return;

        while ((m = _getq(cl->cl_q)) != NULL) {
                PKTCNTR_ADD(&cl->cl_stats.drop_cnt, m_pktlen(m));
                m_freem(m);
                cl->cl_hif->hif_packets--;
                cl->cl_hif->hif_ifq->ifq_len--;
        }
        KKASSERT(qlen(cl->cl_q) == 0);

        update_vf(cl, 0, 0);    /* remove cl from the actlist */
        set_passive(cl);
}

static void
set_active(struct hfsc_class *cl, int len)
{
        if (cl->cl_rsc != NULL)
                init_ed(cl, len);
        if (cl->cl_fsc != NULL)
                init_vf(cl, len);

        cl->cl_stats.period++;
}

static void
set_passive(struct hfsc_class *cl)
{
        if (cl->cl_rsc != NULL)
                ellist_remove(cl);

        /*
         * actlist is now handled in update_vf() so that update_vf(cl, 0, 0)
         * needs to be called explicitly to remove a class from actlist
         */
}

static void
init_ed(struct hfsc_class *cl, int next_len)
{
        uint64_t cur_time;

        cur_time = read_machclk();

        /* update the deadline curve */
        rtsc_min(&cl->cl_deadline, cl->cl_rsc, cur_time, cl->cl_cumul);

        /*
         * update the eligible curve.
         * for concave, it is equal to the deadline curve.
         * for convex, it is a linear curve with slope m2.
         */
        cl->cl_eligible = cl->cl_deadline;
        if (cl->cl_rsc->sm1 <= cl->cl_rsc->sm2) {
                cl->cl_eligible.dx = 0;
                cl->cl_eligible.dy = 0;
        }

        /* compute e and d */
        cl->cl_e = rtsc_y2x(&cl->cl_eligible, cl->cl_cumul);
        cl->cl_d = rtsc_y2x(&cl->cl_deadline, cl->cl_cumul + next_len);

        ellist_insert(cl);
}

static void
update_ed(struct hfsc_class *cl, int next_len)
{
        cl->cl_e = rtsc_y2x(&cl->cl_eligible, cl->cl_cumul);
        cl->cl_d = rtsc_y2x(&cl->cl_deadline, cl->cl_cumul + next_len);

        ellist_update(cl);
}

static void
update_d(struct hfsc_class *cl, int next_len)
{
        cl->cl_d = rtsc_y2x(&cl->cl_deadline, cl->cl_cumul + next_len);
}

static void
init_vf(struct hfsc_class *cl, int len)
{
        struct hfsc_class *max_cl, *p;
        uint64_t vt, f, cur_time;
        int go_active;

        cur_time = 0;
        go_active = 1;
        for ( ; cl->cl_parent != NULL; cl = cl->cl_parent) {
                if (go_active && cl->cl_nactive++ == 0)
                        go_active = 1;
                else
                        go_active = 0;

                if (go_active) {
                        max_cl = actlist_last(cl->cl_parent->cl_actc);
                        if (max_cl != NULL) {
                                /*
                                 * set vt to the average of the min and max
                                 * classes.  if the parent's period didn't
                                 * change, don't decrease vt of the class.
                                 */
                                vt = max_cl->cl_vt;
                                if (cl->cl_parent->cl_cvtmin != 0)
                                        vt = (cl->cl_parent->cl_cvtmin + vt)/2;

                                if (cl->cl_parent->cl_vtperiod !=
                                    cl->cl_parentperiod || vt > cl->cl_vt)
                                        cl->cl_vt = vt;
                        } else {
                                /*
                                 * first child for a new parent backlog period.
                                 * add parent's cvtmax to vtoff of children
                                 * to make a new vt (vtoff + vt) larger than
                                 * the vt in the last period for all children.
                                 */
                                vt = cl->cl_parent->cl_cvtmax;
                                for (p = cl->cl_parent->cl_children; p != NULL;
                                     p = p->cl_siblings)
                                        p->cl_vtoff += vt;
                                cl->cl_vt = 0;
                                cl->cl_parent->cl_cvtmax = 0;
                                cl->cl_parent->cl_cvtmin = 0;
                        }
                        cl->cl_initvt = cl->cl_vt;

                        /* update the virtual curve */
                        vt = cl->cl_vt + cl->cl_vtoff;
                        rtsc_min(&cl->cl_virtual, cl->cl_fsc, vt, cl->cl_total);
                        if (cl->cl_virtual.x == vt) {
                                cl->cl_virtual.x -= cl->cl_vtoff;
                                cl->cl_vtoff = 0;
                        }
                        cl->cl_vtadj = 0;

                        cl->cl_vtperiod++;  /* increment vt period */
                        cl->cl_parentperiod = cl->cl_parent->cl_vtperiod;
                        if (cl->cl_parent->cl_nactive == 0)
                                cl->cl_parentperiod++;
                        cl->cl_f = 0;

                        actlist_insert(cl);

                        if (cl->cl_usc != NULL) {
                                /* class has upper limit curve */
                                if (cur_time == 0)
                                        cur_time = read_machclk();

                                /* update the ulimit curve */
                                rtsc_min(&cl->cl_ulimit, cl->cl_usc, cur_time,
                                    cl->cl_total);
                                /* compute myf */
                                cl->cl_myf = rtsc_y2x(&cl->cl_ulimit,
                                    cl->cl_total);
                                cl->cl_myfadj = 0;
                        }
                }

                if (cl->cl_myf > cl->cl_cfmin)
                        f = cl->cl_myf;
                else
                        f = cl->cl_cfmin;
                if (f != cl->cl_f) {
                        cl->cl_f = f;
                        update_cfmin(cl->cl_parent);
                }
        }
}

static void
update_vf(struct hfsc_class *cl, int len, uint64_t cur_time)
{
        uint64_t f, myf_bound, delta;
        int go_passive;

        go_passive = qempty(cl->cl_q);

        for (; cl->cl_parent != NULL; cl = cl->cl_parent) {
                cl->cl_total += len;

                if (cl->cl_fsc == NULL || cl->cl_nactive == 0)
                        continue;

                if (go_passive && --cl->cl_nactive == 0)
                        go_passive = 1;
                else
                        go_passive = 0;

                if (go_passive) {
                        /* no more active child, going passive */

                        /* update cvtmax of the parent class */
                        if (cl->cl_vt > cl->cl_parent->cl_cvtmax)
                                cl->cl_parent->cl_cvtmax = cl->cl_vt;

                        /* remove this class from the vt list */
                        actlist_remove(cl);

                        update_cfmin(cl->cl_parent);

                        continue;
                }

                /*
                 * update vt and f
                 */
                cl->cl_vt = rtsc_y2x(&cl->cl_virtual, cl->cl_total)
                    - cl->cl_vtoff + cl->cl_vtadj;

                /*
                 * if vt of the class is smaller than cvtmin,
                 * the class was skipped in the past due to non-fit.
                 * if so, we need to adjust vtadj.
                 */
                if (cl->cl_vt < cl->cl_parent->cl_cvtmin) {
                        cl->cl_vtadj += cl->cl_parent->cl_cvtmin - cl->cl_vt;
                        cl->cl_vt = cl->cl_parent->cl_cvtmin;
                }

                /* update the vt list */
                actlist_update(cl);

                if (cl->cl_usc != NULL) {
                        cl->cl_myf = cl->cl_myfadj
                            + rtsc_y2x(&cl->cl_ulimit, cl->cl_total);

                        /*
                         * if myf lags behind by more than one clock tick
                         * from the current time, adjust myfadj to prevent
                         * a rate-limited class from going greedy.
                         * in a steady state under rate-limiting, myf
                         * fluctuates within one clock tick.
                         */
                        myf_bound = cur_time - machclk_per_tick;
                        if (cl->cl_myf < myf_bound) {
                                delta = cur_time - cl->cl_myf;
                                cl->cl_myfadj += delta;
                                cl->cl_myf += delta;
                        }
                }

                /* cl_f is max(cl_myf, cl_cfmin) */
                if (cl->cl_myf > cl->cl_cfmin)
                        f = cl->cl_myf;
                else
                        f = cl->cl_cfmin;
                if (f != cl->cl_f) {
                        cl->cl_f = f;
                        update_cfmin(cl->cl_parent);
                }
        }
}

static void
update_cfmin(struct hfsc_class *cl)
{
        struct hfsc_class *p;
        uint64_t cfmin;

        if (TAILQ_EMPTY(cl->cl_actc)) {
                cl->cl_cfmin = 0;
                return;
        }
        cfmin = HT_INFINITY;
        TAILQ_FOREACH(p, cl->cl_actc, cl_actlist) {
                if (p->cl_f == 0) {
                        cl->cl_cfmin = 0;
                        return;
                }
                if (p->cl_f < cfmin)
                        cfmin = p->cl_f;
        }
        cl->cl_cfmin = cfmin;
}

/*
 * TAILQ based ellist and actlist implementation
 * (ion wanted to make a calendar queue based implementation)
 */
/*
 * eligible list holds backlogged classes being sorted by their eligible times.
 * there is one eligible list per interface.
 */

static ellist_t *
ellist_alloc(void)
{
        ellist_t *head;

        head = kmalloc(sizeof(ellist_t *), M_ALTQ, M_WAITOK);
        TAILQ_INIT(head);
        return (head);
}

static void
ellist_destroy(ellist_t *head)
{
        kfree(head, M_ALTQ);
}

static void
ellist_insert(struct hfsc_class *cl)
{
        struct hfsc_if *hif = cl->cl_hif;
        struct hfsc_class *p;

        /* check the last entry first */
        if ((p = TAILQ_LAST(hif->hif_eligible, _eligible)) == NULL ||
            p->cl_e <= cl->cl_e) {
                TAILQ_INSERT_TAIL(hif->hif_eligible, cl, cl_ellist);
                return;
        }

        TAILQ_FOREACH(p, hif->hif_eligible, cl_ellist) {
                if (cl->cl_e < p->cl_e) {
                        TAILQ_INSERT_BEFORE(p, cl, cl_ellist);
                        return;
                }
        }
        KKASSERT(0); /* should not reach here */
}

static void
ellist_remove(struct hfsc_class *cl)
{
        struct hfsc_if *hif = cl->cl_hif;

        TAILQ_REMOVE(hif->hif_eligible, cl, cl_ellist);
}

static void
ellist_update(struct hfsc_class *cl)
{
        struct hfsc_if *hif = cl->cl_hif;
        struct hfsc_class *p, *last;

        /*
         * the eligible time of a class increases monotonically.
         * if the next entry has a larger eligible time, nothing to do.
         */
        p = TAILQ_NEXT(cl, cl_ellist);
        if (p == NULL || cl->cl_e <= p->cl_e)
                return;

        /* check the last entry */
        last = TAILQ_LAST(hif->hif_eligible, _eligible);
        KKASSERT(last != NULL);
        if (last->cl_e <= cl->cl_e) {
                TAILQ_REMOVE(hif->hif_eligible, cl, cl_ellist);
                TAILQ_INSERT_TAIL(hif->hif_eligible, cl, cl_ellist);
                return;
        }

        /*
         * the new position must be between the next entry
         * and the last entry
         */
        while ((p = TAILQ_NEXT(p, cl_ellist)) != NULL) {
                if (cl->cl_e < p->cl_e) {
                        TAILQ_REMOVE(hif->hif_eligible, cl, cl_ellist);
                        TAILQ_INSERT_BEFORE(p, cl, cl_ellist);
                        return;
                }
        }
        KKASSERT(0); /* should not reach here */
}

/* find the class with the minimum deadline among the eligible classes */
struct hfsc_class *
ellist_get_mindl(ellist_t *head, uint64_t cur_time)
{
        struct hfsc_class *p, *cl = NULL;

        TAILQ_FOREACH(p, head, cl_ellist) {
                if (p->cl_e > cur_time)
                        break;
                if (cl == NULL || p->cl_d < cl->cl_d)
                        cl = p;
        }
        return (cl);
}

/*
 * active children list holds backlogged child classes being sorted
 * by their virtual time.
 * each intermediate class has one active children list.
 */
static actlist_t *
actlist_alloc(void)
{
        actlist_t *head;

        head = kmalloc(sizeof(*head), M_ALTQ, M_WAITOK);
        TAILQ_INIT(head);
        return (head);
}

static void
actlist_destroy(actlist_t *head)
{
        kfree(head, M_ALTQ);
}
static void
actlist_insert(struct hfsc_class *cl)
{
        struct hfsc_class *p;

        /* check the last entry first */
        if ((p = TAILQ_LAST(cl->cl_parent->cl_actc, _active)) == NULL
            || p->cl_vt <= cl->cl_vt) {
                TAILQ_INSERT_TAIL(cl->cl_parent->cl_actc, cl, cl_actlist);
                return;
        }

        TAILQ_FOREACH(p, cl->cl_parent->cl_actc, cl_actlist) {
                if (cl->cl_vt < p->cl_vt) {
                        TAILQ_INSERT_BEFORE(p, cl, cl_actlist);
                        return;
                }
        }
        KKASSERT(0); /* should not reach here */
}

static void
actlist_remove(struct hfsc_class *cl)
{
        TAILQ_REMOVE(cl->cl_parent->cl_actc, cl, cl_actlist);
}

static void
actlist_update(struct hfsc_class *cl)
{
        struct hfsc_class *p, *last;

        /*
         * the virtual time of a class increases monotonically during its
         * backlogged period.
         * if the next entry has a larger virtual time, nothing to do.
         */
        p = TAILQ_NEXT(cl, cl_actlist);
        if (p == NULL || cl->cl_vt < p->cl_vt)
                return;

        /* check the last entry */
        last = TAILQ_LAST(cl->cl_parent->cl_actc, _active);
        KKASSERT(last != NULL);
        if (last->cl_vt <= cl->cl_vt) {
                TAILQ_REMOVE(cl->cl_parent->cl_actc, cl, cl_actlist);
                TAILQ_INSERT_TAIL(cl->cl_parent->cl_actc, cl, cl_actlist);
                return;
        }

        /*
         * the new position must be between the next entry
         * and the last entry
         */
        while ((p = TAILQ_NEXT(p, cl_actlist)) != NULL) {
                if (cl->cl_vt < p->cl_vt) {
                        TAILQ_REMOVE(cl->cl_parent->cl_actc, cl, cl_actlist);
                        TAILQ_INSERT_BEFORE(p, cl, cl_actlist);
                        return;
                }
        }
        KKASSERT(0); /* should not reach here */
}

static struct hfsc_class *
actlist_firstfit(struct hfsc_class *cl, uint64_t cur_time)
{
        struct hfsc_class *p;

        TAILQ_FOREACH(p, cl->cl_actc, cl_actlist) {
                if (p->cl_f <= cur_time)
                        return (p);
        }
        return (NULL);
}

/*
 * service curve support functions
 *
 *  external service curve parameters
 *      m: bits/sec
 *      d: msec
 *  internal service curve parameters
 *      sm: (bytes/tsc_interval) << SM_SHIFT
 *      ism: (tsc_count/byte) << ISM_SHIFT
 *      dx: tsc_count
 *
 * SM_SHIFT and ISM_SHIFT are scaled in order to keep effective digits.
 * we should be able to handle 100K-1Gbps linkspeed with 200Hz-1GHz CPU
 * speed.  SM_SHIFT and ISM_SHIFT are selected to have at least 3 effective
 * digits in decimal using the following table.
 *
 *  bits/sec    100Kbps     1Mbps     10Mbps     100Mbps    1Gbps
 *  ----------+-------------------------------------------------------
 *  bytes/nsec  12.5e-6    125e-6     1250e-6    12500e-6   125000e-6
 *  sm(500MHz)  25.0e-6    250e-6     2500e-6    25000e-6   250000e-6
 *  sm(200MHz)  62.5e-6    625e-6     6250e-6    62500e-6   625000e-6
 *
 *  nsec/byte   80000      8000       800        80         8
 *  ism(500MHz) 40000      4000       400        40         4
 *  ism(200MHz) 16000      1600       160        16         1.6
 */
#define SM_SHIFT        24
#define ISM_SHIFT       10

#define SM_MASK         ((1LL << SM_SHIFT) - 1)
#define ISM_MASK        ((1LL << ISM_SHIFT) - 1)

static __inline uint64_t
seg_x2y(uint64_t x, uint64_t sm)
{
        uint64_t y;

        /*
         * compute
         *      y = x * sm >> SM_SHIFT
         * but divide it for the upper and lower bits to avoid overflow
         */
        y = (x >> SM_SHIFT) * sm + (((x & SM_MASK) * sm) >> SM_SHIFT);
        return (y);
}

static __inline uint64_t
seg_y2x(uint64_t y, uint64_t ism)
{
        uint64_t x;

        if (y == 0)
                x = 0;
        else if (ism == HT_INFINITY)
                x = HT_INFINITY;
        else
                x = (y >> ISM_SHIFT) * ism + (((y & ISM_MASK) * ism) >> ISM_SHIFT);

        return (x);
}

static __inline uint64_t
m2sm(u_int m)
{
        uint64_t sm;

        sm = ((uint64_t)m << SM_SHIFT) / 8 / machclk_freq;
        return (sm);
}

static __inline uint64_t
m2ism(u_int m)
{
        uint64_t ism;

        if (m == 0)
                ism = HT_INFINITY;
        else
                ism = ((uint64_t)machclk_freq << ISM_SHIFT) * 8 / m;
        return (ism);
}

static __inline uint64_t
d2dx(u_int d)
{
        uint64_t dx;

        dx = ((uint64_t)d * machclk_freq) / 1000;
        return (dx);
}

static u_int
sm2m(uint64_t sm)
{
        uint64_t m;

        m = (sm * 8 * machclk_freq) >> SM_SHIFT;
        return ((u_int)m);
}

static u_int
dx2d(uint64_t dx)
{
        uint64_t d;

        d = dx * 1000 / machclk_freq;
        return ((u_int)d);
}

static void
sc2isc(struct service_curve *sc, struct internal_sc *isc)
{
        isc->sm1 = m2sm(sc->m1);
        isc->ism1 = m2ism(sc->m1);
        isc->dx = d2dx(sc->d);
        isc->dy = seg_x2y(isc->dx, isc->sm1);
        isc->sm2 = m2sm(sc->m2);
        isc->ism2 = m2ism(sc->m2);
}

/*
 * initialize the runtime service curve with the given internal
 * service curve starting at (x, y).
 */
static void
rtsc_init(struct runtime_sc *rtsc, struct internal_sc *isc, uint64_t x, uint64_t y)
{
        rtsc->x = x;
        rtsc->y = y;
        rtsc->sm1 = isc->sm1;
        rtsc->ism1 = isc->ism1;
        rtsc->dx = isc->dx;
        rtsc->dy = isc->dy;
        rtsc->sm2 = isc->sm2;
        rtsc->ism2 = isc->ism2;
}

/*
 * calculate the y-projection of the runtime service curve by the
 * given x-projection value
 */
static uint64_t
rtsc_y2x(struct runtime_sc *rtsc, uint64_t y)
{
        uint64_t x;

        if (y < rtsc->y) {
                x = rtsc->x;
        } else if (y <= rtsc->y + rtsc->dy) {
                /* x belongs to the 1st segment */
                if (rtsc->dy == 0)
                        x = rtsc->x + rtsc->dx;
                else
                        x = rtsc->x + seg_y2x(y - rtsc->y, rtsc->ism1);
        } else {
                /* x belongs to the 2nd segment */
                x = rtsc->x + rtsc->dx
                    + seg_y2x(y - rtsc->y - rtsc->dy, rtsc->ism2);
        }
        return (x);
}

static uint64_t
rtsc_x2y(struct runtime_sc *rtsc, uint64_t x)
{
        uint64_t y;

        if (x <= rtsc->x) {
                y = rtsc->y;
        } else if (x <= rtsc->x + rtsc->dx) {
                /* y belongs to the 1st segment */
                y = rtsc->y + seg_x2y(x - rtsc->x, rtsc->sm1);
        } else
                /* y belongs to the 2nd segment */
                y = rtsc->y + rtsc->dy
                    + seg_x2y(x - rtsc->x - rtsc->dx, rtsc->sm2);
        return (y);
}

/*
 * update the runtime service curve by taking the minimum of the current
 * runtime service curve and the service curve starting at (x, y).
 */
static void
rtsc_min(struct runtime_sc *rtsc, struct internal_sc *isc, uint64_t x, uint64_t y)
{
        uint64_t y1, y2, dx, dy;

        if (isc->sm1 <= isc->sm2) {
                /* service curve is convex */
                y1 = rtsc_x2y(rtsc, x);
                if (y1 < y)
                        /* the current rtsc is smaller */
                        return;
                rtsc->x = x;
                rtsc->y = y;
                return;
        }

        /*
         * service curve is concave
         * compute the two y values of the current rtsc
         *      y1: at x
         *      y2: at (x + dx)
         */
        y1 = rtsc_x2y(rtsc, x);
        if (y1 <= y) {
                /* rtsc is below isc, no change to rtsc */
                return;
        }

        y2 = rtsc_x2y(rtsc, x + isc->dx);
        if (y2 >= y + isc->dy) {
                /* rtsc is above isc, replace rtsc by isc */
                rtsc->x = x;
                rtsc->y = y;
                rtsc->dx = isc->dx;
                rtsc->dy = isc->dy;
                return;
        }

        /*
         * the two curves intersect
         * compute the offsets (dx, dy) using the reverse
         * function of seg_x2y()
         *      seg_x2y(dx, sm1) == seg_x2y(dx, sm2) + (y1 - y)
         */
        dx = ((y1 - y) << SM_SHIFT) / (isc->sm1 - isc->sm2);
        /*
         * check if (x, y1) belongs to the 1st segment of rtsc.
         * if so, add the offset.
         */
        if (rtsc->x + rtsc->dx > x)
                dx += rtsc->x + rtsc->dx - x;
        dy = seg_x2y(dx, isc->sm1);

        rtsc->x = x;
        rtsc->y = y;
        rtsc->dx = dx;
        rtsc->dy = dy;
}

static void
get_class_stats(struct hfsc_classstats *sp, struct hfsc_class *cl)
{
        sp->class_id = cl->cl_id;
        sp->class_handle = cl->cl_handle;

        if (cl->cl_rsc != NULL) {
                sp->rsc.m1 = sm2m(cl->cl_rsc->sm1);
                sp->rsc.d = dx2d(cl->cl_rsc->dx);
                sp->rsc.m2 = sm2m(cl->cl_rsc->sm2);
        } else {
                sp->rsc.m1 = 0;
                sp->rsc.d = 0;
                sp->rsc.m2 = 0;
        }
        if (cl->cl_fsc != NULL) {
                sp->fsc.m1 = sm2m(cl->cl_fsc->sm1);
                sp->fsc.d = dx2d(cl->cl_fsc->dx);
                sp->fsc.m2 = sm2m(cl->cl_fsc->sm2);
        } else {
                sp->fsc.m1 = 0;
                sp->fsc.d = 0;
                sp->fsc.m2 = 0;
        }
        if (cl->cl_usc != NULL) {
                sp->usc.m1 = sm2m(cl->cl_usc->sm1);
                sp->usc.d = dx2d(cl->cl_usc->dx);
                sp->usc.m2 = sm2m(cl->cl_usc->sm2);
        } else {
                sp->usc.m1 = 0;
                sp->usc.d = 0;
                sp->usc.m2 = 0;
        }

        sp->total = cl->cl_total;
        sp->cumul = cl->cl_cumul;

        sp->d = cl->cl_d;
        sp->e = cl->cl_e;
        sp->vt = cl->cl_vt;
        sp->f = cl->cl_f;

        sp->initvt = cl->cl_initvt;
        sp->vtperiod = cl->cl_vtperiod;
        sp->parentperiod = cl->cl_parentperiod;
        sp->nactive = cl->cl_nactive;
        sp->vtoff = cl->cl_vtoff;
        sp->cvtmax = cl->cl_cvtmax;
        sp->myf = cl->cl_myf;
        sp->cfmin = cl->cl_cfmin;
        sp->cvtmin = cl->cl_cvtmin;
        sp->myfadj = cl->cl_myfadj;
        sp->vtadj = cl->cl_vtadj;

        sp->cur_time = read_machclk();
        sp->machclk_freq = machclk_freq;

        sp->qlength = qlen(cl->cl_q);
        sp->qlimit = qlimit(cl->cl_q);
        sp->xmit_cnt = cl->cl_stats.xmit_cnt;
        sp->drop_cnt = cl->cl_stats.drop_cnt;
        sp->period = cl->cl_stats.period;

        sp->qtype = qtype(cl->cl_q);
#ifdef ALTQ_RED
        if (q_is_red(cl->cl_q))
                red_getstats(cl->cl_red, &sp->red[0]);
#endif
#ifdef ALTQ_RIO
        if (q_is_rio(cl->cl_q))
                rio_getstats((rio_t *)cl->cl_red, &sp->red[0]);
#endif
}

/* convert a class handle to the corresponding class pointer */
static struct hfsc_class *
clh_to_clp(struct hfsc_if *hif, uint32_t chandle)
{
        int i;
        struct hfsc_class *cl;

        if (chandle == 0)
                return (NULL);
        /*
         * first, try optimistically the slot matching the lower bits of
         * the handle.  if it fails, do the linear table search.
         */
        i = chandle % HFSC_MAX_CLASSES;
        if ((cl = hif->hif_class_tbl[i]) != NULL && cl->cl_handle == chandle)
                return (cl);
        for (i = 0; i < HFSC_MAX_CLASSES; i++)
                if ((cl = hif->hif_class_tbl[i]) != NULL &&
                    cl->cl_handle == chandle)
                        return (cl);
        return (NULL);
}

#endif /* ALTQ_HFSC */